| 摘要 |
PROBLEM TO BE SOLVED: To provide the production process of well-oriented platelike spinel-type ferrite powdery particles which are appropriately used as a radio wave absorptive material or electromagnetic-shielding material. SOLUTION: This production process for producing the objective platelike spinel-type ferrite powdery particles, consists of a first stage and a second stage. The first stage comprises: adding a water-soluble salt of Ni or its aqueous solution to an aqueous liquid suspension of platelike hematite powdery particles; thereafter, adjusting the pH of the resulting suspension to 9.0-14.0; aging this suspension at 0-30 deg.C to coat the surface of each of platelike hematite particles with hydroxide or oxide of Ni; and thereafter, calcining the coated hematite particles at 500-700 deg.C by heating them to obtain powdery particles of an Ni-containing platelike calcined material. The second stage comprises: adding a water-soluble salt of Ni or its aqueous solution to an aqueous liquid suspension of the Ni-containing platelike calcined material powdery particles obtained in the stage 1; thereafter, adjusting the pH of the resulting suspension to 9.0-14.0; aging this suspension at 0-30 deg.C to coat the surface of each of the Ni-containing platelike calcined material powdery particles with hydroxide or oxide of Ni; and thereafter, firing the coated powdery particles at 800-1,200 deg.C by heating them to obtain platelike spinel-type ferrite powdery particles. |
